Tuesday, June 28, 2005

Jewish thermodynamics, fossil fuel, and geothermal and solar energy

For a couple of daf yomi weeks, we’ve read about the Jewish laws of thermodynamics. Ok, not exactly, but the Talmud faces a dilemma: every kid wants a hot lunch, but Scripture tells us not to light a fire on Shabbos. Assuming delicious cold soups had not yet been invented, what’s a balabusta to do?

<The basic problem is entropy. It’s the second law of thermodynamics. . Not as good as the first law, but we try harder. Closed systems lose heat. So, a coal or wood fire gradually burns out unless, against the shabbos laws, you keep fueling it or stoking the embers. Serving hot food for Friday night is no problem, but a hot lunch for Saturday is a challenge.

Entropy signifies the breakdown in the order of a system. Given the breakdown in my daf yomi blogging, here are notes on Chapter 2 of masechet Shabbat. Perhaps the following thoughts will coalesce into a larger commentary, or maybe you can warm up these leftovers and make something substantial. Disclosure: this was cross-posted in Quicksilver כספית.

1. Although rabbinic rules aim to prevent cooks from stoking a fire on shabbat, Rabbi Oshaya argues that such rules are not needed for hot dishes which improve as they condense. This creates a virtual definition for cholent. (bShab 37a) Turnips and meat are eligible cholent ingredients, but not figs and dates, which taste entropically worse. Some rabbis find shivelled eggs to be delicious.

2. Not all fuels are alike because some fuels, e.g. straw, do not create coals. (38b) Also, new technologies require the rabbis to formulate rules for a range of cooking ranges.

3. Solar energy cannot be used to cook eggs on the Sabbath, if it requires the heating of a derivative cooking surface, like sand or scarves (?!). (Note: Semi-hardboiled eggs may be tested by rolling, a trick I learned as a child, thank you Mom). However, it seems that a device (magnifying glass?) that concentrated the solar heat directly onto an egg would be permissible. Depending on the Jewish/Israeli demand for hard-boiled eggs on Shabbat, this may be a good opportunity for a solar energy entrepreneur. (38b-39a) Rabbinic law restricts fossil fuels yet makes a special exemption for solar energy technologies. (?)

4. Heating system entrepreneurs did come to Tiberias, where they set up hot water plumbing with the use of local hot springs. However, the sages forbade even this automated geothermal heating system because it heats up cold water in a manner analogous to manual fossil fuel methods. (39b) A similar precautionary measure (gezerah) is enacted to prohibit regular hot baths on shabbat, even with water heated previously. New geothermal technologies do not negate the overall need for investing in energy conservation on Shabbat.

5. At first, the sages forbade the use of manmade steambaths as well as bathing in the Tiberian hot springs. However, the Tiberians would not stand this injunction and kept using the springs. Therefore, the rabbis rescinded the order against use of the natural springs, but retained it against artificially heated steambaths. (bShab 40a) This incident reflects an important self-regulating principle of halakhah, which expects the rabbis not to make rulings that the people cannot abide by.

6. The talmudic analysis recognizes the net caloric difference between pouring hot water into cold and cold water into hot. (I remember that we had such problems in physics class but I forget how to solve them.) (bShab 42a) Though lacking instrumentation, the rabbis did try to measure and benchmark the points at which the target material and heat source would result in an act of cooking. (40b)

7. [For further analysis: intentionality and the principle of double effect. According to Rabbi Shimon, unless a prohibited consequence is inevitable, one could continue a permitted activity as long as the forbidden result is not intended. 41b-42a]

8. Thermodynamic properties entail variations in the capacity of materials to insulate or intensify heat. (39b) (Thankfully, this topic can be deferred for further unpolished notes on chapter three!)

Tentative hypothesis: The rabbis were aware of some basic thermodynamic properties and relationships. They differentiated between geothermal, solar and fossil fuel-based energy. They understood heat loss. However, they lacked the level of scientific knowledge and instrumentation that we have today to measure and formally conceptualize thermodynamic systems. Nevertheless, it is likely that they would have understood the greenhouse effect and global warming. Given their capacity to enact precautionary measures (gezerot), therefore, wouldn’t they have pushed for strong global warming legislation, at least* for Saturdays?

Kaspit כספית

* Joking aside, since global warming may have serious health consequences, Jewish law would not limit the necessary energy consumption restrictions to Saturdays. Perhaps the observance of Shabbat, which incidentally reduces fuel use, may inspire Jewish support and inventiveness for sound energy policy.

Sunday, June 26, 2005

Amulets and health

To a modern reader of Shabbat 53b, the Rabbis are dealing with a problem of correlation: Do amulets protect the health of animals? If amulets truly correlate with health, then they may be carried on Shabbat. If there is merely a spurious correlation between amulets and health, then they do not work and carrying them is (or ought to be) a form of prohibited sabbatical work.

Lacking biochemical (etc.) knowledge of sickness, the Rabbis judged the efficacy of amulets by two critera (bShab 61): medical efficacy and expertise. First, amulets are deemed effective if they cure or prevent sickness three times (3x); Second, healers are deemed experts if their amulets cure three times (3x). Wisely, the rabbis did not assume that amulets that cured humans would necessarily work with animals.* For those of us scientifically inclined, we would not expect these criteria to adequately identify effective cures. Fortunately, Jewish law here is judging the amulets only in terms of Shabbat. So the downside to an error is rather limited (esp for a shogeg). In Quicksilver כספית, this daf inspired me to blog more about the problem of mercury in vaccines, where the stakes are higher.

* Starting with the gemara at bShab 61a-b, the Talmudic liberature applies the 3x criteria with permutations involving 3 different amulets, diseases, patients, or healers.